Process for pumping vapors under high vacuum



Sept. ZO, 1932. w. K. L Ewls PROCESS FOR PUMPING VAPORS UNDER HIGH VACUUM Filed July 28, 1928 NUYWOK QR nSnNQ bbb @imm UZNU Patented Sept. 20, 129.."2

UNITED STATES PATENT OFFICE WARREN K. LEWIS, OF NEWTON, MASSACHUSETTS, ASSIGNOR TO STANDARD OIL DEVELOPMENT COMPANY, A CORPORATION 0F DELAWARE PROCESS FOR PUMPING VAPORS UNDER HIGH VACUUM Application med my as, 1928. semi No. 296,006.

10 drawing which illustrates the invention.

The drawing is a semi-diagrammatic view in sectional elevation of an apparatus ar' ranged for the extraction of oil vapors from gas or oil wells operated under high vacua.

15 In my copending applications Serial Nos.

296,007 and 296,008, filed July 28, 1928, methods for obtaining high vacua in oil wells, gas wells and the like were disclosed. The present method finds a ready and valuable appli- 20 cation for the same purpose, namely for obtaining an increased yield of'natural gas and naphtha from gas wells, although my present method is of great value in other processes.

I have observed that certain vapors unlike steam do not, on adiabatic compression, become superheated, but on the contrary condense and the vapor of normally liquid hydrocarbons, such as pentane, hexane, benzene, toluene and the like are of this nature. It is needless to say that cooling of the pump cylinders increases the condensation. I have further observed that vacuum pumps when pumping such vapors, particularly at high vacua, operate with avolumetric eihciency greatly below that obtained when operating on non-condensible gases under the same pressure. My present method greatly increases the capacity of any given pump and makes it possible to obtain higher'vacua than are now commercially realized.

Referring to the drawing, numeral 1 denotes the casinghead of a gas or oil well which is being operated at a high vacuum, for example, 28.5 to 29 inches of mercury below atmospheric pressure or higher. It will be understood that operation at such high vacua has not been heretofore practical. A pipe 2 conducts the vaporous mixture from the Well to a vacuum pump 3 which may be of v10 to storage (not shown).

one or more stages, although a single stage unit is shown on the drawing for simplicity. A pipe 4 is shown connected to pipe 2 for introduction of inert gas. The drawing shows only the compression cylinder which is provided with valve chest 3a. The compressed mixture is discharged through a pipe 7 to cooler 8 and thence to separator drum 9 from which the condensate is 'removed by line The uncondensed gas is removed by line 11 to a suitable apparatus or removing the remaining gasoline or low boiling liquid hydrocarbons from the gas. The extraction system is shown generally at 12 and may be a compression and coollng process, an absorption'process, an adsorption process or, indeed, any known method for removing'the normally liquid constituents from the gas. The extracted gasoline is removed by line 13 to storage (not shown) and the ducted back by pipe 4 or recirculation through thecompressor. Gas may be bled from the system for fuel or for other uses by line 14.

In the operation of my process the vaporous mixture is removed from the well under high vacuum, for example 1/;, inch of mercury absolute pressure or less, and is fed to the vacuum pump `together with a regulated quantity of non-condensible gas, such as nitrogen, CO2 or hydrocarbon gas. Inert gases are preferred-to air, although the latter could be used. Ordinarily the Volume of gas is from 10 to 100% of the volume of the vapor and the amount may be regulated so that substantially no condensation occurs within the pump, although the cylinders are as may be concooled according to the present practice. Ad-

for each case.

As an example of my process, a pump, which is capable of reducing the pressure in a closed air filled vessel to 0.7 inches of mercury absolute pressure, is tested pumping air at approximately 1.0 inch of mercury pressure and the volumetric efficiency was found to be 8.8%. The same pump is then tested pumping toluene vapor substantially free of air or inert gas under the same pressure and it is found to have an efficiency of 1.75%. That is to say, the pump handles about five times as much air as toluene under the same pressure conditions. When air is admixed with the toluene vapor in a proportion of .4 volumes of air per volume of toluene vapor, the efficiency rises to 7.65%, and if the efficiency is based on the vapor alone, neglecting the volume of air, the value is found to be 5.4%; or in other words, the volume of toluene vapor handled is increased about threefold by the addition of the air.

Although my specification has particularly described the process in relation to the removal of gas and oil vapor from wells, it will be understood that my invention finds application wherever it is desirable to pump vapors which, unlike steam, do not superheat on adiabatic compression or such compression as occurs in compression pumps cooled in any suitable manner.

My invention is not to be limited by any theory of the operation of the process, nor by any example which may have been given merely by way of illustration, but only by the following claims in which l Wish to claim all novelty inherent in the invention.

I claim:

1. The method of compressing through a vacuum pump vapors which condense on adiabatic compression, which comprises actuating the vacuum pump adiabatically to draw the vapors from a body thereof in' a confined stream under less than atmospheric pressure, adding to the confined stream on the intake side of the pump gas which does not condense on adiabatic compression whereby condensation is lessened at pressures greater than the pressure in the intake, and delivering the mixture from the pump under said increased pressure.

2. The method of compressin through a vacuum pump vapors which con ense an adiabatic compression, which comprises actuating the vacuum pump adiabatically to draw the vapors `in a confined stream from a body thereof under less than atmospheric pressure, adding to the confined stream on the intake side of the pump at least 10 percent by v olume of gas which does not condense on adiabatic compression to lessen condensation at atmospheric pressure, and delivering the mixture from the pumping operation under at' least atmospheric pressure.

4. The method of increasing the flow of vapors from a well, which comprises mecha-nically drawing vapors from the well under vless than atmospheric pressure by an adiabatically operated vacuum pump, adding to the vapors gas which does not condense on adiabatic compression to lessen condensation at pressures greater' than the pressures on the intake of the pump, and discharging the mixture from the pump under said increased pressure.

5. The method of increasing the flow of vapors from a Well which comprises mechanically drawing vapors from the Well under less than atmospheric pressure by an adiabatically operated vacuum pump, adding to the vapors gas which does not condense on adiabatic compression to prevent condensation at atmospheric pressure, and discharging the mixture from the pumping operation under at least atmospheric pressure.

WARREN K. LEWIS. 

